Table 2. Combination index (CI) and dose reduction index (DRI) values for HDACi (vorinostat, panobinostat, entinostat or VPA) and 5′-DFUR combination treatment.

cell lines	aCI50 ± SD	aCI75 ± SD	bDRI at IC50 ± SD
	vorinostat + 5′DFUR	vorinostat + 5′DFUR	vorinostat	5′-DFUR
SKBR3	0.63 ± 0.23	0.70 ± 0.21	3.42 ± 1.70	3.8 ± 1.82
MDA-MB231	0.98± 0.27	1.02± 0.1	3.46 ± 1.7	1.34 ± 0.62
MDA-MB468	0.49 ± 0.13	0.50 ± 0.14	2.64 ± 0.78	10.62 ± 4.1
MCF-7	0.71 ± 0.10	0.71 ± 0.068	2.67 ± 0.65	3 ± 1.10
	panobinostat + 5′DFUR	panobinostat + 5′DFUR	panobinostat	5′-DFUR
SKBR3	0.73 ± 0.15	0.71 ± 0.2	3.43 ± 1.76	3.44 ± 1.73
MDA-MB231	0.99 ± 0.4	0.93 ± 0.4	2.56 ± 1.07	2.17 ± 1.67
MDA-MB468	0.53 ± 0.2	0.58 ± 0.15	4.58 ± 2.7	5.45 ± 1.25
MCF-7	0.58 ± 0.16	0.61 ± 0.094	3.08 ± 1.72	4.5 ± 1.99
	entinostat + 5′DFUR	entinostat + 5′DFUR	entinostat	5′-DFUR
SKBR3	0.76 ± 0.01	0.74 ± 0.10	4.38 ± 2.28	2.44 ± 1.29
MDA-MB231	1.12 ± 0.04	1.26 ± 0.20	1.35 ± 0.24	2.92 ± 1.15
MDA-MB468	0.55 ± 0.045	0.54 ± 0.022	3.32 ± 1.56	3.0 ± 0.84
MCF-7	0.75 ± 0.16	0.76 ± 0.11	1.46 ± 0.36	14.5 ± 3.59
MCF-10A	1.22 ± 0.14	1.57 ± 0.036	1.53 ± 0.32	1.81 ± 0.10
	VPA + 5′DFUR	VPA + 5′DFUR	VPA	5′-DFUR
SKBR3	0.63 ± 0.14	0.59 ± 0.2	2.89 ± 1.5	4.45 ± 2.12
MDA-MB231	1.04 ± 0.037	1.06 ± 0.066	2.06 ± 0.36	1.71 ± 0.42
MDA-MB468	0.61 ± 0.17	0.65 ± 0.083	2.81 ± 1.27	5.81 ± 2.9
MCF-7	0.59 ± 0.24	0.56 ± 0.2	2.39 ± 0.76	6.45 ± 4.62
MCF-10A	1.11 ± 0.19	1.11 ± 0.18	0.99 ± 0.17	8.39 ± 7.13

^aCI values (mean ± SD from at least three separate experiments performed in quadruplicates) computed at 50 and 75% of cell kill (CI₅₀ and CI₇₅, respectively) according by CalcuSyn software after 96 hours of treatment. Combinations were considered strongly synergistic when CIs were below 0.9.

^bDRI values (mean ± SD from at least three separate experiments performed in quadruplicates) represents the order of magnitude (fold) of dose reduction obtained for IC₅₀ (DRI₅₀) in combination setting compared with each drug alone.

Abbreviations: VPA (valproic acid); 5′-DFUR (5′-deoxy-5-fluorouridine)